DESCRIPTION: (Adapted for the investigators's abstract) The primary objective of the proposed research is to characterized and understand the molecular, cellular and biochemical events that occur following exposure of human epithelial cells to genotoxic agents. It is thought that the persistence of certain DNA base modifications alter gene expression which may change the stage of cellular differentiation and directly contribute to the transformed state. The hypothesis of the study is that genotoxins cause a change in the differentiated state of the normal cell which may be a precursor to the transformed phenotype. Thus, the role of DNA damage and repair in the modulation of selected genes involved in cellular differentiation will be addressed in human liver epithelial cells. These liver cell cultures are easily subpassed, replicatively active and exhibit many of the in vivo organ "specific biochemical and differentiated functions. These can provide data relevant to the normal human liver and other human epithelial tissues. The present focus of this project will be to characterize the specific carcinogen DNA adducts associated with changes in the genes for alpha-fetoprotein (FP)_, gamma-glutamyl transpeptidase (GFT), glucose-6- phosphatase (G6P) and cytokeratins in these cells that go on to transformation. These genes are associated with live specific cellular function and differentiation, and alternations in these proteins occur during the initial stages of chemically induced hepatocarcinoma. It is hoped that the proposed studies will provide new information and insights into the mechanisms that lead to human cell genotoxicity.